Current systems and methods for generating an array of spots on an inclined surface may not provide a required level of performance. For example, in some systems the spot arrangement may be tangential, meaning that the spots are largely aligned with the tangential direction of a spiral scanning stage movement along with a small tilt. A drawback of tangential spot placement is that the pitch (the difference of scanning radius between adjacent spots) may not be exactly identical for all of the spots even when the spots are essentially equally spaced. This uneven spacing may be referred to as the “pitch error”. The pitch error may be minimal for a surface having a large radius, such as the edge of a large wafer, but the pitch error may increase near the center of the wafer. The pitch error may change as the spots scan the wafer from the edge of the wafer to the center of the wafer, which can make the pitch error difficult to correct. Although ways to compensate for the pitch error do exist, these options may result in some loss of sensitivity or throughput for the system.
Therefore, there exists a need for improved systems and methods for generating an array of spots on an inclined surface.